My invention relates to a shoring device comprising a piston, cylinder, and an outer ratcheting collar combined with an inner ratcheting ring. More particularly, this invention relates to a shoring device with a moveable outer ratcheting collar, and which collar interlocks within an inner ratcheting ring over the piston and cylinder. My new outer ratcheting collar insures that the partially enclosed piston.
In experimental trials, my pneumatic shoring device withstood pneumatic pressures within the cylinder of at least 300 psi (pounds per square inch) for a minimum of fifteen seconds. My new device is intended for, but not exclusively, public works and construction, rescue and other projects in which shoring is necessary.
As workers shore trenches, they must quickly install shoring to prevent collapse of the trench walls. If shoring is not installed, soil cohesion is lost and it becomes almost impossible to maintain a safe trench. The prior art as best depicted in expired U.S. Pat. No. 3,851,856(Berg) provided a shoring device with an inlet connecting to a pressure source for expanding the device tightly against trench walls. There is also a rotational outer ratcheting ring mounted on one cylinder end, which receives the piston.
This rotational outer ratcheting ring extends axially from the cylinder and surrounds a proximal piston end.
Still referring to the Berg device, the rotational member is prevented from rotation in part by a cam-like ridge along the proximal member edge. Subsequent to cylinder pressurization the piston remains extended by securing the cam-like ridge on the rotational member with an abutting cam pin. However the only structure in Berg""s device which prevents the piston from random axial movement projectile is a small diameter pin. This small diameter pin penetrates the rotational member and abuts the cylinder, after the abutting cam pin is already in place. The small diameter pin end abuts the cylinder, and can be further tightened against the cylinder by a t-bolt.
The disadvantage of Berg is that this small diameter pin is the only opposing frictional and mechanical force which maintains the piston in an extended position after the gas pressure is removed. Also this pin""s force is only perpendicular to the long axis of the piston and cylinder. In contrast, my new shoring device comprises an inner-ratcheting ring which, in combination with an outer ratcheting collar, maintains the piston in an extended position. This inner ratcheting ring preferably attaches to the cylinder with allen screws (threaded with hexagonal head depressions), as well as a circular metal lip which engages one cylinder end. The inner ratcheting ring reduces the likelihood that the piston becomes a projectile. This safety feature occurs because the piston abuts the inner lip, and so the piston cannot move laterally.
The outer removable ratcheting collar encloses the inner ratcheting ring and interlocks with inner ratcheting ring serrations. Outer ratcheting collar preferably comprises one rectangular protrusion which interlocks with the inner serrated ring. This interlocking prevents counter-clockwise rotation of the outer ratcheting collar thereby preventing collapse of the piston upon the sound or floor.
My improved shoring device is engineered to assist underground workers in compliance with the OSHA regulation governing excavations, i.e., 29 C.F.R. 1926.650. This group includes, but is not limited to, sewer contractors, plumbers, gas companies, telephone companies, municipal public works departments and fire rescue services. The principle goal of my shoring device is to provide the necessary physical support which ensures a work environment safe from collapse.
In particular, shoring is the placement of crossbracing and other components within a trench to support trench walls. There are two important theories of shoring: first is the theory of xe2x80x9czero-movementxe2x80x9d, in which shoring is designed to prevent wall movement. Shoring is not sufficiently strong to retain a moving wall of soil: it merely prevents a soil wall from initially moving. The second theory of shoring is designated the xe2x80x9cArch Effect.xe2x80x9d Shoring is effective because it creates forces as it pushes again trench walls. The network of crossbraces and uprights or wale-plates creates an arch effect which retains soil. The shoring and crossbracing actually retains soil, and not the plywood or sheeting.
An operator applies plywood or sheeting to prevent surface soil from falling and injuring a worker. To achieve xe2x80x9czero movementxe2x80x9d and the xe2x80x9carch effect,xe2x80x9d all gaps and voids must be filled where the crossbrace bears on the trench wall. Other than the mandatory inspection for damage before each use and an occasional cleaning, there are no maintenance requirements.
My preferred pneumatic shoring device also comprises a contiguous series of pressurized gas channel through the cylinder of the piston. This contiguous pressurized gas channel includes a circular channel segment along the lower floor surface of a cylinder endcup.
My improved shoring device is much safer than, yet remains just as cost effective, as the prior art. The new crucial safety feature comprises an outer ratcheting collar in combination with an inner ratcheting ring, both of which concentrically enclose a cylinder which contains a piston. Any loosening of the piston through rotational counterclockwise movement requires the installer""s deliberate act of manually depressing a thumblock. This thumblock disengages outer ratcheting collar from the inner ratcheting ring. In addition, an inner ratcheting ring greatly reduces the likelihood that the piston will become a projectile. This is because the rubber piston cup cannot move past the circular lip along the inner ratcheting ring.
The piston is cylindrical in shape and inserts within the larger diameter cylinder (which is also cylindrical in shape). The piston also comprises a plurality of aligned apertures, into which a metal camming pin inserts. This metal camming pin, in combination with a camming surface, prevents the piston from retracting into the cylinder, once the air pressure is removed. This metal camming pin provides initial adjustment whenever an operator rotates the outer ratcheting collar during installation of the shoring device. Fine adjustment subsequently occurs whenever the outer ratcheting collar interlocks with the enclosed inner-ratcheting ring.
Testing of my shoring device in the preferred pneumatic embodiment confirms that it is stronger than any conceivable soil load. See 29 C.F.R. 1926.652. In particular, the inner ratcheting ring comprises a plurality of serrations, and there is a corresponding locking protrusion within the outer ratcheting collar. The inner ratcheting ring encloses the proximal cylinder end, and this ring is further attached to the cylinder with at least two screws.
With my shoring device, engagement with an inner ratcheting ring occurs automatically upon clockwise rotation of outer ratcheting collar. In contrast, release of outer ratcheting collar requires the operator""s depression of a thumblock. In contrast, the interlocked position of the outer ratcheting collar requires no act by the operator. The initial lateral extension of my assembled improved shoring device occurs whenever pressurized air enters the cylinder during a trench application. For support of a car an unstable or building, my shoring device is manually extended until resistance is felt, and then the outer ratcheting collar is locked.
During removal of an installed shoring device, there is counter-clockwise release of the outer ratcheting collar prior to removal of the air pressure. In actual field operations, air pressure is not removed from the shoring device until the operator has moved to a safe position removed from the device.
Each shoring device also comprises two removable swivel sideplates. One sideplate reversibly attaches to the most distal piston end, while the other similarly attaches to the most proximal cylinder end. My removable swivel sideplates comprise adjustable setscrews for engagement of wood shoring boards or aluminum wale-plates. Each preferred setscrew is approximately xc2xc inch in diameter, and comprises twenty threads per inch. Each preferred setscrew is also approximately one inch in length. However, other sideplates or end adapters are also within the scope of my invention, and may be even preferably for primarily vertical or angled applications, such as buildings or vehicles.
My preferred pneumatic shoring device also comprises a cylinder plug. Cylinder plug is hollow at its proximal end to accommodate one removable swivel sideplate. The remaining approximate one-half of the cylinder plug is solid metal and comprises a continuous channel for compressed air. A novel feature of my modified cylinder plug is a cylinder rubber endcup at its distal plug end. Cylinder rubber endcup more efficiently prevents air leaks from the air channel segments within metal cylinder plug. In the preferred embodiment and best mode, the cylinder endcup comprises apertures and a circular channel, which contribute to the most efficient airflow from cylinder plug distal end. More preferably, this air channel segment lies along the lower floor surface of the cylindrical rubber endcup.
This circular channel segment comprises a contiguous aperture through which pressurized air from a gas inlet evenly and quickly seals the raised edge of a piston rubber endcup. In contrast, the prior art comprises a circular groove around the circumference of the metal cylinder plug, and into which groove a rubber O-ring is inserted. The problem with this prior art approach is breakage of the o-ring upon metal groove edges, and subsequence leakage of air from the cylinder plug.
My preferred improved shoring device is assembled by inserting the piston so that its piston rubber endcup initially abuts cylinder rubber endcup. The inner ratcheting ring is next inserted over the cylinder end until its circular metal lip engages the distal cylinder end. Inner ratcheting ring is then bolted to the cylinder. Outer ratcheting collar is next positioned so that it encloses inner ratcheting ring.
The outer ratcheting collar has limited movement along the cylinder, but it can be manually rotated and then locked to inner serrated ring. At least approximately one-third of the longitudinal axial length of the piston must always remain within the cylinder. After the outer ratcheting collar fits over the inner serrated ring, the operator finally inserts the removable swivel sideplates at the distal and proximal end of the shoring device.
My pneumatic shoring device for use in trenches is the preferred embodiment.
It is another goal of my invention to provide a more uniform distribution of pressurized air by providing a circular channel segment within the cylinder.
It is another goal of my invention to provide an anti-projectile feature to prevent the piston from ejecting from the cylinder.
It is another goal of my invention to provide cast aluminum handles for manual rotation of outer ratcheting collar.